1. Field of the Invention
The present invention relates to a system for controlling the operation of a body implantable device which is operable to act upon the body in response to changes in a physiological parameter sensed by a physiological sensor. The sensor includes transmission circuitry for transmitting a signal related to the parameter sensed to the device which is operable to decipher the signal and act accordingly upon the body.
2. Description of the Prior Art
Heretofore various implantable devices, such as a pacing device, have been proposed that control parameters that are programmable by using external programming devices, e.g., parameters such as rate of pacing and A-V delay. Also, circuitry has been provided for changing the controlled parameter with programming codes. Example of such previously proposed devices are disclosed in the following patents:
______________________________________ U.S. PAT. NO. PATENTEE ______________________________________ 3,777,762 Nielsen 3,830,242 Greatbatch 4,223,679 Schulman et al. 4,226,244 Coury et al. 4,228,803 Richards 4,236,525 Sluetz et al. 4,313,441 Buffet 4,316,472 Mirowski et al. ______________________________________
The Nielsen U.S. Pat. No. 3,777,762 discloses a pacemaker having an output control circuit which is adapted, when activated, to control pacing pulses in such a manner that the amplitude of each pulse is slightly less than that of the preceding pulse. The control circuit can be activated and deactivated from outside the body, either by suitable hospital equipment, or manually by a surgeon. The control circuit ascertains the smallest pacing pulse that causes heart contraction thereby to permit a threshold value of the heart to be determined without surgical operation.
The Greatbatch U.S. Pat. No. 3,830,242 discloses a remotely operated control system for controlling operation of an electrical pulse generator, such as a cardiac pacer, having timing circuitry for controlling the generation of pulses and signal responsive circuitry for resetting the timing circuitry in response to ventricular electrical signals. The system also includes a portable transmitter operable to selectively generate r.f. signals having different envelope durations. A circuit responsive to the r.f. signals is coupled to the pulse generator and is operable to detect, rectify and filter the r.f. signals and then produce corresponding command signals for causing an increase or decrease in the rate of pulse generation.
The Schulman et al. U.S. Pat. No. 4,233,679 discloses an FM/FM or FM/AM modulated telemetry signal generator for supplying a control signal to a living tissue stimulator implanted in a body. The signal generator includes an externally located oscillator that is controlled by impedance changes in an impedance reflecting circuit located in the implantable tissue stimulator.
The Coury et al. U.S. Pat. No. 4,226,244 discloses a preformed electrical connector for use with a body implantable stimulator, such as heart pacemaker, having a signal generator. The stimulator, e.g., a pacer, has one or two electrical leads electrically and mechanically connected to the pulse generator through one or two preformed electrical connectors mounted in the pacer body containing the signal generator.
The Rickards U.S. Pat. No. 4,228,803 discloses a cardiac pacemaker having means for automatically adjusting the rate of operation to correspond to physiological changes. Circuitry is provided for detecting the presence or absence of an evoked T wave following a delivered stimulus pulse, and for measuring the time interval between the stimulus pulse and the following T wave. The escape interval from the pacemaker pulse generator is varied in accordance with the detected stimulus T interval and in the same direction so as to vary the pacing rate in accordance with variations in such interval. Since this interval in turn corresponds to physiological changes, the pacemaker is adapted to automatically follow the patient's physiological changes. Here signals are sensed from the pacemaker itself without the use of special detectors for sensing conditions elsewhere in the body.
The Sluetz et al. U.S. Pat. No. 4,236,525 discloses an apparatus and method for manually altering the function of distal electrodes of a body implantable tissue stimulator assembly. In one exemplary embodiment, the polarity of the distal electrodes may be reversed by axially repositioning the proximal connectors within the female connector assembly of a tissue stimulator.
The Buffet U.S. Pat. No. 4,313,441 discloses a process for regulating, by means of an extra-corporeal control unit, an implanted cardiac stimulator comprising a pulse generator and a pair of electrodes. The stimulator is controlled so that it functions at a fixed rhythm independent of normal cardiac rhythm. The extra-corporeal unit detects successive pulses emitted by the stimulator. After each of the selected stimulator pulses detected, and during the whole period between successive stimulator pulses, a train of successive control pulses is transmitted by the extra-corporeal control unit and is received by the stimulator. No train of successive control pulses is transmitted during the whole period between other successive stimulator pulses
The Mirowski et al. U.S. Pat. No. 4,316,472 discloses an externally controlled implantable electronic device for delivering a cardioverting pulse of energy to the atrium of an ailing heart. In one embodiment, the device is particularly suited for use when the patient visits the office of his physician, and contemplates the transmission of both information and powering energy through the skin of the patient. In another embodiment, the device can be readily operated at home, by the patient, and without the intervention of the physician. Here the source of energy is permanently implanted.
As will be described in greater detail hereinafter, the system for controlling a body implantable action device of the present invention differs from the systems previously proposed by providing a remote sensor that is capable of sensing physiological parameters, that is coupled directly or indirectly to the body implantable device, and that generates programming codes for controlling the operating parameters of the body implantable device such as a pacemaker. In one embodiment of the present invention, the remote sensor is electrically coupled to a transmitter which sends electrical signals, which can be radio frequency signals, to the action device such as a pacemaker, and wherein a distal electrode of a pacing lead acts as an antenna to pick up and transmit the radio signals to the pacemaker.